The primary objective of this investigation is to determine the possible relationship of lysosomal hydrolases to aging of the lens and cataractogenesis, using a Wistar rat strain known to develop aging-related cataracts (posterior subcapsular; deep cortical) which have a morphological resemblance to human forms of the disease. The appropriateness of the CFN Wistar and Hannover Wistar rat strains, which demonstrate equivalent biomicroscopic lens abnormalities during cataract development, as models for human senile cataractogenesis has been described. Wistar rat lenses exposed to cataractogenic X-ray doses will serve as an additional model. The approach used in these investigations will be: (1) to assay biochemically the activities of certain lysosomal enzymes that have been implicated in lens proteolysis, as well as acid phosphatase, a lysosomal marker enzyme; (2) to localize, and to assess the amount and distribution of the hydrolases in sections through specific lens regions using microanalytical histochemical techniques; and (3) to correlate histopathological changes with histochemical and biochemical changes in concentration and distribution of lysosomal hydrolases.